G'day guys,
I have pulled this question from one of Bobs exams. I completed the calcs using ETAS and used the closest answer, but none of them were completely correct for me.
In the answer sheet, it seems ETAS has not been applied. Can someone please tell me why I don't apply ETAS in this instance?

Thanks,
PJ

The cited question contains two typos.

(a) answer (a) should read 158 nm - just finger trouble which was corrected towards the bottom of the solution

(b) the typo at (a) has been transcribed from the incorrect distance calculation but the correct number has been used in the time calculation - just one of those things which slips through to the keeper on occasion.

Keep in mind that the correct solution is always to use ETAS. If you choose to use the TAS approximation below 10 degrees, you will get a small error, in this case around 2 knots. Given that there is absolutely no reason to use that approximation (as the ETAS value is there for you to read off the computer), you should use the correct solution, which is to read off ETAS and correct it for the wind component to get the G/S.

I ran the sums both on a Dalton and a CR and arrived at the same answers, using the correct ETAS solution with the CR.

You might like to review the recent ETAS thread at www.bobtait.com.au/forum/performance/7386-etas-lost-at-sea

Hi John,
Thanks for clearing that up. I found it weird that the answer working didn't use ETAS and I thought "what the hell have I missed now!?"
I'm using CR3 and hadn't had a problem previously. Thanks for clearing up another error in the course.
Cheers

Thanks for that I have amended the answer in the book

Cheers

Many thanks for that Stuart.
Cheers